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Genetically determined molecular weight differences in murine complement component C6
Insights
CBA mice possess two forms of complement component 6 (C6), types A and B, while BALB/c and DBA/2 mice only have type A. The high molecular weight type B C6 is an autosomal dominant trait.
Area of Science:
- Immunogenetics
- Complement System Biology
- Biochemistry
Background:
- Complement component 6 (C6) is crucial for the formation of the membrane attack complex.
- Genetic variations in complement proteins can impact immune responses and disease susceptibility.
- Previous studies have identified different molecular forms of complement proteins in various species.
Purpose of the Study:
- To investigate the molecular heterogeneity of complement component 6 (C6) in different mouse strains.
- To characterize the biochemical properties and inheritance patterns of C6 variants.
- To establish a genetic basis for C6 polymorphism in mice.
Main Methods:
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to separate C6 by molecular weight.
- Erythrocyte/agarose overlay gels to detect hemolytic activity of C6 bands.
- Flatbed isoelectric focusing (IEF) to determine C6 charge variants.
- Functional assays to confirm hemolytic activity of separated C6 forms.
- Cross-breeding experiments to analyze inheritance patterns.
Main Results:
- CBA mouse plasma exhibited two C6 forms: type A (Mr ~90,000) and type B (Mr ~100,000).
- BALB/c and DBA/2 mouse plasma contained only type A C6.
- Isoelectric focusing revealed distinct pI values for type A and type B C6, with CBA plasma showing two hemolytic band sets.
- Breeding experiments indicated that the high molecular weight type B C6 is inherited as an autosomal dominant trait.
Conclusions:
- Mouse complement component 6 (C6) exists in at least two molecular forms (A and B) with distinct molecular weights and isoelectric points.
- The presence of high molecular weight type B C6 is controlled by an autosomal dominant gene.
- This genetic polymorphism in C6 may have implications for understanding immune system variation in mice.
Abstract:
Plasma samples from male CBA, BALB/c and DBA/2 mice were subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Bands of C6 hemolytic activity in the washed resolving gel were identified by means of an erythrocyte/agarose overlay gel. CBA plasma was found to contain two forms of C6, one with a molecular weight (Mr) of approximately 90 000 (type A) and one with a Mr of 100 000 (type B); CBA mice were thus designated C6: A+B+. BALB/c and DBA/2 plasma on the other hand contained only the low molecular weight type A C6 and were designated C6: A+B-. Flat bed isoelectric focusing followed by functional overlays showed that CBA plasma produced two sets of hemolytic bands (pI 5.25-5.4 and 5.0-5.2) whereas BALB/c and DBA/2 plasma produced only the more cathodal band set. The additional band set in CBA plasma corresponded to the high-Mr type B C6. Results of breeding experiments demonstrated that the possession of the high Mr type B C6 was inherited in the manner of an autosomal phenotypically dominant characteristic.